Problems working with 8bpp and 24bpp images

[SkripT]

Hi. First, I post the code that finally I have implemented using the code by Cesar. After I comment a problem with this code:

void FotoEditorFotos::paintRect(const QColor &color, const QRect &rectAPintar)
{
	int xMin = rectAPintar.x();
	int xMax = xMin + rectAPintar.width() - 1;
	int yMin = rectAPintar.y();
	int yMax = yMin + rectAPintar.height() - 1;
 
	if (!imatge.valid(xMin, yMin) || !imatge.valid(xMax, yMax)) return;
 
	QRgb colorRgb = color.rgba();
 
	quint8 *pixelsLiniaFoto;
	quint8 color8, colorVermell, colorVerd, colorBlau, colorAlpha;
 
	int bytesPixel = (imatge.depth()) >> 3;
 
	if (bytesPixel == 1)
		color8 = (imatge.isGrayScale()) ? qGray(colorRgb) : obtenirIndexColor(valorColor);
	else
	{
		colorVermell = qRed(colorRgb);
		colorVerd = qGreen(colorRgb);
		colorBlau = qBlue(colorRgb);
		colorAlpha = qAlpha(colorRgb);
	}
 
	for (int j = yMin; j <= yMax; j++)
	{
		pixelsLiniaFoto = static_cast<quint8 *>(imatge.scanLine(j)) + (xMin * bytesPixel);
 
		for (int i = xMin; i <= xMax; i++)
		{
			switch (bytesPixel)
			{
                     // Qt only manages 1, 8 or 32bpp
				case 1:
					*(pixelsLiniaFoto++) = color8;
					break;
 
				case 4:
					*(pixelsLiniaFoto++) = colorVermell;
					*(pixelsLiniaFoto++) = colorVerd;
					*(pixelsLiniaFoto++) = colorBlau;
					*(pixelsLiniaFoto++) = colorAlpha;
					break;
			}
		}
	}
 
	update();
}

void FotoEditorFotos::paintRect(const QColor &color, const QRect &rectAPintar)
{
	int xMin = rectAPintar.x();
	int xMax = xMin + rectAPintar.width() - 1;
	int yMin = rectAPintar.y();
	int yMax = yMin + rectAPintar.height() - 1;

	if (!imatge.valid(xMin, yMin) || !imatge.valid(xMax, yMax)) return;

	QRgb colorRgb = color.rgba();

	quint8 *pixelsLiniaFoto;
	quint8 color8, colorVermell, colorVerd, colorBlau, colorAlpha;

	int bytesPixel = (imatge.depth()) >> 3;

	if (bytesPixel == 1)
		color8 = (imatge.isGrayScale()) ? qGray(colorRgb) : obtenirIndexColor(valorColor);
	else
	{
		colorVermell = qRed(colorRgb);
		colorVerd = qGreen(colorRgb);
		colorBlau = qBlue(colorRgb);
		colorAlpha = qAlpha(colorRgb);
	}

	for (int j = yMin; j <= yMax; j++)
	{
		pixelsLiniaFoto = static_cast<quint8 *>(imatge.scanLine(j)) + (xMin * bytesPixel);

		for (int i = xMin; i <= xMax; i++)
		{
			switch (bytesPixel)
			{
                     // Qt only manages 1, 8 or 32bpp
				case 1:
					*(pixelsLiniaFoto++) = color8;
					break;
				
				case 4:
					*(pixelsLiniaFoto++) = colorVermell;
					*(pixelsLiniaFoto++) = colorVerd;
					*(pixelsLiniaFoto++) = colorBlau;
					*(pixelsLiniaFoto++) = colorAlpha;
					break;
			}
		}
	}

	update();
}

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The problem is that with images with 32bpp it paints the area that I want but with an invalid color, different from the color that I pass to the function. Anoybody could explain where's the mistake?

[Cesar]

The only problem I could imagine is the following: your imatge object uses the different places for colours, rather then RGBA. I suggest you to temporarily the code to

//[SKIP]
case 4:
    *(pixelsLiniaFoto++) = 0xff;
    *(pixelsLiniaFoto++) = 0x00;
    *(pixelsLiniaFoto++) = 0x00;
    *(pixelsLiniaFoto++) = 0x00;
//[SKIP]

//[SKIP]
case 4:
    *(pixelsLiniaFoto++) = 0xff;
    *(pixelsLiniaFoto++) = 0x00;
    *(pixelsLiniaFoto++) = 0x00;
    *(pixelsLiniaFoto++) = 0x00;
//[SKIP]

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and watch for the results. This way you will fill the QRect with the pure color. Let's pretend you have got blue QRect. Then your first line should be changed to

*(pixelsLiniaFoto++) = colorBlau;

*(pixelsLiniaFoto++) = colorBlau;

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This way you can check, which colour is the first, which is the second and what is the place of alpha channel

[SkripT]

Thanks again Cesar, it's really strange if I try to put the value 255 in one posistion and the rest at 0, the result is always the same. It paints the selection with the same gray color. I attach an image of the result.